This invention relates to the jetting of ink and, more particularly, the jetting of phase change ink.
The use of phase change ink is particularly desirable since it produces high quality print with a high degree of resolution, e.g., good edge definition and contrast.
Co-pending application Ser. No. 610,627, filed May 16, 1984, discloses a hot melt or phase change ink. The ink is elevated in temperature as it leaves the jet so as to be in the liquid state; upon or shortly after contact with target, the ink solidifies or freezes on the target. Typically, the dot of ink formed by a droplet of phase change ink protrudes from the target such that the dot may be readily discerned by touch with very little spreading of the dot on the surface of the target. Moreover, because of the substantially instant freezing of the droplet on the target, actual penetration of the droplet into the target which may comprise paper is minimized, at least as compared with other ink jet inks which are not of the phase change type.
As a consequence of the substantially instantaneous freezing of the droplet, the lack of spreading of the droplet after contact with the target, multiple droplets of phase change ink may be necessary to form a mark or dot of the desired size on a target. Although this technique, which is described in co-pending applications Ser. No. 453,295, filed Dec. 27, 1982, and Ser. No. 600,875, filed Jan. 23, 1986 as a continuation of Ser. No. 600,785, filed Apr. 16, 1984 and now abandoned, assigned to the assignee of this invention, does produce high quality printing satisfying to the eye, it does require a higher frequency of droplet ejection to achieve the same rate of printing achieved when using an ink which is not of the phase change type. Moreover, a greater volume of phase change ink may be required to achieve the same visual effect which could be achieved with ink of a non-phase change type.